This invention relates generally to the venting of exhaust gases and the supply of combustion air for gas fired boilers. More particularly, the invention is directed to a termination unit for terminating separate side by side vent and air supply pipes extending through a side wall of a building which contains the boiler.
The flue gases of a gas fired boiler may be exhausted through the roof, through a chimney or through a side wall of the building containing the boiler. When venting of the combustion gases is through a side wall, it is common practice for air supply piping to be provided in order to furnish outside air to the boiler for the combustion process. Typically, the vent piping and the air supply piping are arranged concentrically.
In a concentric pipe installation, the outside pipe must be rather large in diameter in order to provide both pipes with sufficient size. The need for a large pipe leads to the requirement for a large hole size and also necessitates a large radius for the bends in the piping. A large bend radius requires considerable room to achieve and is particularly disadvantageous where space is a problem such as when floor joints are near the side wall penetration location. Another problem with concentric pipe systems is that an inner plenum in the boiler is required for the transition between the two piping runs. This complicates the boiler construction and increases the cost of the boiler. The materials that can be used for the air pipe are also limited in a concentric pipe arrangement because of the proximity of the air pipe to the vent pipe. Other problems are that special fittings are often required and the length of the piping runs is limited.
The inlet end of the air supply pipe often requires active elements in order to assure an adequate air volume. Additionally, phenomena such as frost and foreign material clogging of the air intake can create problems. Provision must also be made at times for draft problems caused by an overhanging roof or other overhangs. Acidic condensates and other chemical agents in the flue products can corrode and otherwise damage the components of the termination structure unless special materials are used.